This invention relates to a colored marker ink to be used on a writing board of black or a dark color for the purpose of producing thereon opaque marker traces.
The marker inks available today on the market are chiefly of the type intended for use on white writing boards. These marker inks for use on white writing boards produce transparent marker traces when applied to the boards. When such a marker ink is used on a writing board which happens to be black or of a dark color, the surface of the writing board shows through the marker traces deposited on the board because of the transparency of the ink, with the result that the letters or figures written with the ink are obscured by the color of the underlying writing board possibly to the extent of being illegible. Thus, these conventional marker inks cannot be effectively used for the purpose of writing letters or figures on surfaces which are black or of dark colors.
One of the conventional types of marker inks formulated to produce opaque letters or figures on writing surfaces is known to resort to dispersion of a pigment in the ink composition. This particular type of marker ink produces opaque marker traces on a writing surface owing to the dispersion of pigment particles throughout the ink composition. When such an opaque marker is used in writing letters on a writing surface, the pigment particles dispersed in the ink composition settle directly onto the finely rugged contour of the writing surface and form the marker traces. When the letters thus written are erased by wiping, those pigment particles settling in the finely rugged contour of the writing surface cannot readily be wiped out so that perfect erasure of the marker traces is impossible.
A quick-drying writing ink has already been proposed (U.S. Pat. No. 3,486,912). This quick-drying ink is directed solely to ensuring the rapidity with which the ink applied to the writing paper dries. It is not intended to form on the writing board opaque traces which can be readily erased.
An electrostatic printing ink has also been proposed (U.S. Pat. No. 3,280,036). This is an ink obtained by dispersing a dye in water and is not a solvent-type ink.
There has further been proposed a fiber-pen ink which comprises a resin, a good solvent for the resin having a high speed of vaporization and a non-solvent for the resin having a lower speed of vaporization than the good solvent mentioned above (British Pat. No. 1,311,154). This ink is intended primarily to prevent the nib of the pen from drying up while the pen is not in use.
An object of the present invention is to provide a marker ink which forms clear colored marker traces on a writing board, particularly a writing board which is black or of a dark color.
Another object of this invention is to provide a marker ink which forms on the writing board marker traces capable of being readily wiped off the board surface.